Reverse Osmosis Applications Research Articles

Chlorine-resistant sulfochlorinated and sulfonated polysulfone for reverse osmosis membranes by coating method

In this work, sulfochlorinated polysulfone (SC-PSf), a functional polysulfone with chlorine resistance, was synthesized through metalation sulfochlorination of polysulfone (PSf). For endowing the required hydrophilicity of SC-PSf, the sulfonyl chloride groups on SC-PSf were partially hydrolyzed to sulfonic groups to produce sulfonated SC-PSf (SC-S-PSf). Thin film composite (TFC) membranes for reverse osmosis application were fabricated by coating solution of SC-S-PSf on porous PSf substrate and then crosslinked by piperazine (PIP) to form polysulfone-sulfamide (PSSA) skin layer. In order to enhance the spreadability of polymer solution on PSf supporting layer, tetrabutylammonium chloride (TBAC), a common surfactant, was added into the coating solution. A flawless membrane was acquired only by a single coating step and at dilute SC-S-PSf solution when TBAC was added into polymer solution. Through optimizing coating conditions, the NaCl rejection and water flux of PSSA membrane reached 96.9% and 17.8 L/m2h under brackish desalination conditions. Moreover, the PSSA membrane exhibited the long-term stability against chlorine during the operation condition of 2000 ppm NaOCl for 10 days. The salt rejection of PSSA only decreased by 1%. In contrast, the salt rejection of polyamide membrane decreased by 8% under the same condition.

Application of reverse osmosis and nanofiltration techniques at municipal drinking water facilities

Main disadvantages of state of the art membrane techniques are discussed with respect to the problem of concentrate disposal. Possible ways to improve conventional membrane techniques and to radically decrease the number of effluents discharged are proposed. Application of newly developed “open channel” membrane modules that do not contain “dead” areas enables us to develop and implement into practice new techniques to reduce and even utilize concentrates of membrane units. Experiments demonstrated a possibility to reduce concentrate flow due to deposition of excessive calcium as calcium carbonate on seed crystals in the reactor. Flow diagrams for different cases of natural water composition are described and discussed that demonstrate newly developed techniques to produce drinking quality water using reverse osmosis and nanofiltration membrane facilities with high recoveries.

Improving performance of low pressure reverse osmosis systems by intermittent autoflushing

Improving performance of low pressure reverse osmosis systems by intermittent autoflushing Scaling formation on the membrane surface in the form of calcium carbonate, calcium sulphate, silica, and/or magnesium silicate is a main problem of the reverse osmosis (RO) application for upgrading low grade water. Scaling in RO system is generally controlled by softening the feed water, limiting the recovery and/or the addition of antiscalants which is impractical for household RO system. In this work, the feasibility of intermittent autoflushing to prevent scale formation in household RO systems was investigated. All experiments were carried out using commercially available RO membrane (CSM RE-1812LP) which operated for 6 hours under operating pressure 5 kg/cm2 and total recycle operating mode. Model solution of feed water contain CaCl2 and NaHCO3 were prepared to meet various LSI values in the range of 0 to 1.5. Duration and interval time of autoflush were in the range of 60 to 15 s and 5 to 60 min respectively. The results shown that the permeate flux of the system which operated using intermittent autoflushing relatively stable. It is emphasized that intermittent autoflushing may improve the performance of household reverse osmosis systems.Keywords: Autoflushing, scaling, physical cleaning, reverse osmosis Abstrak Pembentukan kerak (scaling) pada permukaan membran berupa kerak kalsium karbonat, kalsium sulfat, silika dan atau magnesium silikat merupakan permasalahan utama pada aplikasi sistem membran reverse osmosis (RO) pada proses pemurnian air. Scaling pada sistem RO umumnya dikontrol dengan melakukan pretreatment terhadap air umpan seperti softening, menambahkan zat antiscalant pada saat proses pemisahan serta membatasi tingkat recovery, dimana proses-proses tersebut tidak praktis apabila diaplikasikan pada sistem RO skala rumah tangga. Penelitian ini bertujuan untuk melihat kemungkinan metode intermittent autoflush dapat diaplikasikan untuk menghambat terjadinya scaling pada sistem RO skala rumah tangga. Penelitian ini dilakukan dengan menggunakan satu unit membran spiral wound jenis CSM RE-1812LP yang dioperasikan dengan tekanan operasi 5 kg/cm2 dan waktu operasi ± 6 jam. Larutan umpan sintesis dibuat dengan melarutkan CaCl2 dan NaHCO3 hingga nilai LSI mencapai kisaran 0-1,5. Durasi dan interval dari metode intermittent autoflush divariasikan pada kisaran 60-15 detik dan 5-60 menit. Hasil penelitian menunjukkan bahwa fluks permeat relatif stabil pada sistem RO yang menggunakan metode intermittent autoflush. Hal ini menandakan bahwa metode intermittent autoflush ini dimungkinkan untuk meningkatkan kinerja dari sistem RO skala rumah tangga.Kata Kunci: Autoflushing, scaling, physical cleaning, reverse osmosis

ECOTOXICOLOGICAL EVALUATION THROUGH ALLIUM CEPA OF FOOD INDUSTRY EFFLUENT TREATED BY PROCESS USING MEMBRANES

Due to population growth, there is an increase in the tendency of water resource degradation. One of the biggest polluters is the practice of dumping industrial and domestic effluents without any treatment on the watercourse. The utilization of effluents is an alternative to minimize the inadequate waste dump, thus avoiding the overload on the treatment system as well as cutting down costs and expenses. This work’s objective is to evaluate the application of reverse osmosis in a food industrial effluent, in physicochemical and toxicological terms. A reverse osmosis technical application was conducted and then the effluent was examined, before and afterward, in terms of pH, Turbidity, Colouring, Conductivity, Dissolved Oxygen, Total Organic Carbon, and Total Nitrogen as well as a toxicological evaluation (Allium cepa). According to the obtained result, it can be identified that the technique of reverse osmosis showed treatment efficiency when applied to the effluent containing coloring and soy isoflavones, with regards to the physicals and chemical evaluation. In terms of toxicological evaluation, with respect to the radicular development, the treated effluent (permeate) showed a radicular growth, once the raw effluent did not develop any root.

Synthesis and characterization of novel Cellulose Nanocrystals-based Thin Film Nanocomposite membranes for reverse osmosis applications

A novel TFN membrane was fabricated by embedding Cellulose Nanocrystals (CNCs) into the polyamide active layer. Membranes were synthesized by in-situ interfacial polymerization of m-phenylenediamine (MPD) and trimesoyl chloride (TMC) containing different amounts of CNCs. Successful incorporation of CNCs into the polyamide layer was confirmed by XRD analyses. Surface morphology of the membranes was characterized by SEM and AFM. Water contact angle measurements showed improved hydrophilicity of the TFN membranes. Desalination experiments with synthetic brackish water at 20 bar(g) revealed doubling of the water flux from 30 to 63 ± 10 L/m2·h, without significantly compromising the salt rejection (97.8%) for 0.1% (w/v) CNCs loading. In the fouling/filtration experiments with 300 ppm of Bovine Serum Albumin (BSA) in the feed solution, the TFN membrane had 11% smaller water flux reduction compared to the control TFC membrane. The promising performance of the CNCs-based TFN membranes and the fact that CNCs are inexpensive and abundant nanoparticles indicates their potential for a large-scale use in water desalination. Moreover, since CNCs are safe and environmentally friendly nanoparticles their possible leaching out during membrane operation would not impose health and environmental concerns.

Optimization of the ionic liquid-based interfacial polymerization system for the preparation of high-performance, low-fouling RO membranes

Thin-film composite (TFC) membranes with a polyamide top layer are a widespread membrane type in reverse osmosis and nanofiltration applications. Despite their good initial performance, they often suffer from a high fouling tendency. A new form of interfacial polymerization, in which ionic liquids (ILs) are introduced as the non-aqueous reaction phase, was developed in our previous work. This resulted in a more sustainable TFC membrane preparation and an enhanced performance. In this work, the improved fouling resistance of these membranes was proven. Moreover, different steps in the synthesis were analyzed to further enhance time and cost efficiency, as well as environmental impact of the preparation process. Time efficiency was improved by shortening the interfacial polymerization time to 10 s, while waste generation was drastically lowered by recycling the IL for consecutive interfacial polymerization cycles. Moreover, residual trimesoyl chloride (TMC) in the IL could also be recycled, since the IL protected the TMC from being hydrolyzed, even at very high water contents in the IL (> 1000 ppm). Successful introduction of the recycling step, together with the possibility to dry the formed membrane sheets without loss of performance by conditioning with glycerol, clearly demonstrated the upscaling potential of the new preparation method.

Numerical modelling of acoustic pressure fields to optimize the ultrasonic cleaning technique for cylinders

Fouling build up is a well-known problem in the offshore industry. Accumulation of fouling occurs in different structures, e.g. offshore pipes, ship hulls, floating production platforms. The type of fouling that accumulates is dependent on environmental conditions surrounding the structure itself. Current methods deployed for fouling removal span across hydraulic, chemical and manual, all sharing the common disadvantage of necessitating halting production for the cleaning process to commence. Conventionally, ultrasound is used in ultrasonic baths to clean a submerged component by the generation and implosion of cavitation bubbles on the fouled surface; this method is particularly used in Reverse Osmosis applications. However, this requires the submersion of the fouled structure and thus may require a halt to production. Large fouled structures such as pipelines may not be accommodated. The application of high power ultrasonics is proposed in this work as a means to remove fouling on a structure whilst in operation. The work presented in this paper consists of the development of a finite element analysis model based on successful cleaning results from a pipe fouled with calcite on the inner pipe wall. A Polytec 3D Laser Doppler Vibrometer was used in this investigation to study the fouling removal process. Results show the potential of high power ultrasonics for fouling removal in pipe structures from the wave propagation across the structure under excitation, and are used to validate a COMSOL model to determine cleaning patterns based on pressure and displacement distributions for future transducer array design and optimization.

Application of reverse osmosis in purifying drinking water

In view of the shortage of water resources and the pollution of water environment, the development of efficient water purification technology is one of the effective ways to ensure the safety of drinking water. The technology of reverse osmosis has attracted much attention in the application of drinking water security for its advantages of no phase change and simple equipment. This paper briefly introduces the research progress at home and abroad, basic principles, process flow diagram, advantages and disadvantages and development direction of the technology.

Application of reverse osmosis to treat high ammonia concentrated reject water from sewage sludge digestion

Application of reverse osmosis to treat high ammonia concentrated reject water from sewage sludge digestion

Recent Progress in Reverse Osmosis (RO) Science and Technology

While writing a book on reverse osmosis, it was realized that there had been remarkable progress in recent years in reverse osmosis science and technology. This is a brief summary in which many aspects of RO are discussed, including membrane material and membrane fabrication, membrane characterization, membrane transport, RO module, RO system design, economics, membrane fouling, RO applications and RO/NF membranes for nonaqueous system.

Tris(hydroxymethyl)aminomethane polyamide thin‐film‐composite antifouling reverse osmosis membrane

ABSTRACTFor the applications of reverse osmosis (RO) process, membrane fouling caused by organic molecule adsorption is still a serious problem which significantly decreases membrane lifespan and increases operation costs. In this present article, we report the thin film composite (TFC) RO membrane functionalized with tris(hydroxymethyl)aminomethane (THAM) using one‐step method for improved antifouling property. The results of surface characterization indicated that THAM was successfully grafted onto the active layer of membrane by covalent linkage. Mult‐hydroxyl‐layer was generated and remained steadily on TFC membrane surface after modification. The contact angle decreased from 75.9 ± 3.0° to 46.9 ± 2.3°, which showed a distinct improvement of membrane surface hydrophilicity after modification. The grafted THAM improved water flux by 28.3%, while salt rejection was almost unchanged in membrane property tests. The modified membranes presented preferable antifouling property to foulants of bovine serum albumin, sodium alginate, and dodecyl trimethyl ammonium bromide than that of pristine membranes during dynamic fouling experiments. The method in this study provided an effective way to improve antifouling property of the polyamide thin‐film‐composite RO membrane. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45891.

The operation of reverse osmosis system with CO2 as a scale inhibitor: A study on operational behavior and membrane morphology

Fouling is one of the acute concerns during the application of reverse osmosis (RO) technology for wastewater reclamation. This study emphasizes the effectiveness of CO2 injection for scale inhibition on the surface of membranes during wastewater reclamation. The main objective of CO2 injection is to reduce pH of feed stream for avoiding inorganic scale precipitation. Two different experimental setups (lab- and pilot-scale) were installed and each was operated with four different RO modules including control (without any scale inhibitor), dosage of antiscalant, CO2 injection and simultaneous dosage of antiscalant and CO2 in an influent line. The pH of influent stream was reduced by CO2 purging at the level of 6 and 5. Data from operational setups, water analysis and morphological study of membrane from each module was used to establish comparative result. In comparison with other modules, the RO modules operated with CO2 were found successful to mitigate the inorganic scale formation on the surface of membrane. Furthermore, the RO modules operated with CO2 presented the successful restoration of system performance with clean-in-place.

The comparative study for scale inhibition on surface of RO membranes in wastewater reclamation: CO2 purging versus three different antiscalants

The application of reverse osmosis (RO) membrane in wastewater reclamation is emerged as a potential technology. As far as the operational conditions are concerned, inorganic fouling is a major challenge for membrane treatment systems. At present various antiscalants and chemicals are commercially available for scale inhibition on the surface of membrane. In an earlier study we found that CO2 can effectively inhibit scale growth on the surface of RO membrane in wastewater reclamation. On the basis of previous study, the scale inhibiting efficiency of CO2 was compared with three commercially available antiscalants. The RO system was operated at constant applied pressure with four different scale inhibition methods including CO2, Flocon 260, Flocon 300 and Kuriverter N-500. The permeate flux decline was considered as an indication of scale growth on the membrane surface. The percent salt rejection and ionic mass balance was used to determine the scaling behavior of the RO modules. Membrane autopsy was done to determine the effect of CO2 and antiscalants on the membrane structure. The experimental data revealed that CO2 can effectively inhibit scale growth as compared with all of three antiscalants. However, the Flocon 260 was found better than other two antiscalants.

Next-Generation Nanoporous Materials: Progress and Prospects for Reverse Osmosis and Nanofiltration

Reverse osmosis and nanofiltration are highly adopted, growing technologies that are used to remove salts and other small molecules in water treatment. Both of these technologies primarily use cross-linked polyamide membranes to achieve the desired separation. Many novel nanoporous materials are being developed as alternatives or complements to polyamides, including graphene, graphene oxide, block copolymers, liquid crystals, aquaporins, and other biologically inspired molecular channels. This article evaluates each of these technologies by (i) reviewing the current progress in each area, (ii) identifying key needs for immediate research, and (iii) evaluating considerations for commercial development. The economic benefits of these technologies in reverse osmosis applications are further reviewed to help frame the expected commercial value proposition.

Probing the thickness and roughness of the functional layer in thin film composite membranes

The thickness and roughness of the functional layer in thin film composite membranes (TFCMs) are important determinants of the membrane performance, whether in reverse osmosis, gas separation or energy applications. This paper describes and compares different techniques for the measurement of these quantities. A new method based on atomic force microscopy (AFM) is developed and compared with techniques based on scanning electron microscopy (FEG-SEM) and profilometry. AFM and profilometry methods allowed a simultaneous determination of thickness and roughness and could be extended for studying the effect of parameters such as support membrane roughness. The methods have been tested on polyamide TFC RO membranes. The membranes were prepared by an interfacial polycondensation technique on polysulfone support, by reaction between m-phenylene diamine and trimesoyl chloride in the organic phase. Based on our earlier work which showed the important role of shear on membrane morphology in such syntheses, preparations both with and without shear were employed. The measurement of thickness using AFM was carried out on specially made membranes in which, by the use of a mask, only a part of the PSF was coated with the PA layer. By scanning a region that contains both the covered and the uncovered parts, thickness values could be obtained. In the second technique, the SEM cross sectional images of TFCMs allowed the determination of the distribution of thickness over the area seleted. In the third, a surface profilometer was used to determine the thickness of de-laminated PA films. The thickness distributions and average thicknesses measured from all three methods matched closely. Overall, these techniques are of great potential in TFC and similar membrane characterization.

Application of reverse osmosis at NPP and verification of the process for primary coolant treatment in temelín nuclear power

Drained primary coolant from nuclear power plants containing boric acid is currently treated in the system of evaporators and by ion exchangers. Reverse osmosis as an alternative process to evaporator was investigated. Using reverse osmosis, the feed primary coolant is separated into two output streams: retentate and permeate. Retentate stream consists of concentrated boric acid solution together with other components, while permeate stream consists of purified water. In the first phase of the project the reverse osmosis modules from several manufactures were tested on a batch laboratory apparatus. Certain modifications to the pH of the feed solution were needed to enable the tested membranes to concentrate the H3BO3 in the retentate stream, separate from the pure water in the permeate stream. Furthermore, the separation capability for other compounds present in primary coolant such as K, Li or NH3 were evaluated. In the final phase of the project the pilot-plant unit of reverse osmosis was tested in nuclear power plant Temelín. It was installed in the Special Purification System SVO-6 for the regeneration of boric acid. The aim of the tests performed in Temelín nuclear power plant was to verify possible use of reverse osmosis for the treatment of primary coolant.

High-performance wholly aromatic polyamide–hydrazides

The review summarizes the various methods of preparing wholly aromatic polyamide–hydrazides (PAHs). Polyhydrazides are a class of polymers that possess in their repeating units one amide (–NHOC–) and one hydrazide (–CONHNHOC–) linking bond between appropriate aromatic nuclei. The review provides several figures of different molecular structures of PAH and expounds the methods of polymerization, low, high temperature, and phosphorylation polycondensation methods. Polyhydrazides exhibit some unique and potentially useful properties such as outstanding thermal and thermo-oxidative resistance, very high mechanical strength, and ultrahigh moduli. PAHs undergo structural transformation into poly(amide-1,3,4-oxadiazole)s upon heating, which are also considered highly thermally stable polymers. The review presents a description of the structure–property relation of PAHs. The application of PAHs in reverse osmosis applications has been discussed, as well as the preparation of fibers and metallized PAHs films. Modification of the PAH with carbon nanotubes and graphene and the future prospects for PAHs were introduced with comprehensive references pertaining to this area of research.

Performances of some NF and RO membranes for desalination of MBR treated wastewater

In recent years, because of both lowered discharge limits and reduction of usable water sources, reutilization of water became inevitable. This situation makes the application of advanced water treatment technologies compulsory. In this study, applicability of nanofiltration (NF) and reverse osmosis (RO) methods was investigated for reuse of industrial wastewater treated with advanced treatment method at organized industrial zone. For this purpose, two NF (HL-GE and DL-GE) and one RO (AG-BWRO) membranes were used at 10bar of applied pressure. Permeability test revealed that HL membrane exhibited the highest permeability with 7.22±0.79L/m2hbar of permeability constant followed by AG membrane with a permeability constant of 6.03±0.25L/m2hbar. Less permeable membrane was DL with a permeability constant of 2.08±0.11L/m2hbar. In terms of rejection performance, conductivity, salinity, chemical oxygen demand (COD), total organic carbon (TOC), color, divalent ions (Ca2+, Mg2+ and SO42−) and monovalent ions (Na+, K+, Cl− and HCO3−) were rejected by HL membrane with an average rejection of 37.2±2.1%, 38.6±2.5%, 72.5±5.5%, 79.9±6.1%, 85.4±1.2%, 86.0±0.5%, 88.8±0.3%, 99.9±0.0%, 46.0±0.9%, 27.0±0.3% 17.9±1.1%, 64.3±2.8%, respectively. The respective rejections by DL membrane were 31.1±0.8%, 31.2±1.1%, 36.8±16.4%, 68.2±7.3%, 81.0±4.0%, 77.9±0.7%, 84.7±07%, 99.9±0.0%, 41.0±04%, 18.4±1.7%, 14.0±1.3%, and 45.2±2.7%. On the other hand, higher water quality was obtained with AG-BWRO membrane. AG-BWRO achieved conductivity, salinity, COD, TOC and color rejections of 96.8±0.2%, 96.9±0.1%, 74.7±2.8%, 90.5±4.8% and 87.6±1.9%, respectively. Divalent ions and monovalent ions were rejected by AG-BWRO membrane with an average rejection of higher than 94%. In conclusion, AG-BWRO membrane was found to be the best membrane considering both product water quality and quantity. DL membrane was found to be the worst one among the three membranes investigated in this work.

Application of reverse osmosis to petrochemical industry wastewater treatment aimed at water reuse

PurposeThe purpose of this paper is to apply reverse osmosis (RO) to the treatment of industrial wastewater from a large petrochemical complex in Southern Brazil, in order to verify the conditions of liquid effluent reuse and improve them, especially to reduce the consumption of natural water by some production structures such as boilers and cooling towers.Design/methodology/approachThe petrochemical wastewater was submitted to pretreatment using a sand filter and activated carbon filters. Tests were conducted using RO equipment with a production capacity of 0.25 m3h−1 composed of a spiral membrane module with a membrane area of 7.2 m². Pressures of 8, 12 and 15 bar were applied with reject flow maintained constant at 10 Lm−1.FindingsThe experiment results indicated optimum RO performance since more than 90 percent extraction was obtained for most of the compounds present in the petrochemical wastewater.Originality/valueBy checking the aspects involved, as well as providing some relevant considerations about, this study promotes the application of RO to get a satisfactory water reuse in similar industries, thereby decreasing both the volume of water extracted from wellsprings and the amount of wastewater released into water bodies.

Preparation and Properties of Nanocomposite MWCNTs/Polyamide Reverse Osmosis Membrane for Desalination by Interfacial Polymerization

Thin film nanocomposite (TFN) polyamide (PA) reverse osmosis (RO) membranes incorporating carboxylic multiwall carbon nanotubes (c-MWCNTs) were successfully synthesized by interfacial polymerization with aqueous solution of m-phenylenediamine (MPD) containing c-MWCNTs and Isopar G solution of trimesoly chloride (TMC). In order to improve the dispersion of MWCNTs in polymer matrix, carboxylic groups was modified onto the pristine MWCNTs by acid mixture (sulfuric acid and nitric acid of 3:1 volume ratio) and mixture of sulfuric acid and hydrogen peroxide (4:1 volume ratio). The feasibility of carboxylic on MWCNTs was evaluated by FT-IR, SEM, TEM and Raman spectroscopy analysis. Apparent size distribution and suspension of c-MWCNTs showed the well dispersion condition of c-MWCNTs in water which also proved the successful carboxylic of MWCNTs. The effect of c-MWCNTs incorporation into the PA selective layer on the surface morphology, separation performance and antifouling properties of the membranes were investigated and discussed. The “leaf-like” and granules outgrowth morphology of nanocomposite was observed by SEM and the c-MWCNTs incorporated in PA layer were observed by TEM. After doping c-MWCNTs, the water flux of TFN membranes increased due to higher hydrophilicity and additional water pathways of c-MWCNTs. It is noteworthy that the TFN membrane with 0.005 wt% c-MWCNTs could exhibit water flux as high as 68.3 L·m-2·h-1 and the NaCl rejection maintained at 96.0%. Meanwhile, the TFN membrane with 0.005 wt% c-MWCNTs showed better antifouling affinity than c-MWCNTs free membrane due to the increased in hydrophilicity as well as surface negative charge. Based on the result, it can be concluded that incorporating an appropriate amount of c-MWCNTs into PA rejection layer could potentially improve the performance of TFN membrane during RO applications.